


Frilly Undersans

by Tooth, trinuska



Series: Bonefucker Sanstasies [21]
Category: Undertale (Video Game)
Genre: Dom/sub, Established Relationship, Fluff and Smut, Lesbian Sex, Lingerie, Other, Plot What Plot/Porn Without Plot, Polyamory, Skeletons, magical ghost vagina, sans being romantic is really just him picking up his socks for once lmao
Language: English
Status: Completed
Published: 2016-09-23
Updated: 2016-09-23
Packaged: 2018-08-16 20:44:09
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,871
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/8116945
Author URL: https://archiveofourown.org/users/Tooth/pseuds/Tooth, https://archiveofourown.org/users/trinuska/pseuds/trinuska
Summary: It's you and Sans. You make love.A lot of loveful fluff mixed with explicit pornography.Reader has a vagina, no defining pronouns are used.This is part 21 of a series that has some sort of continuity going on, for the whole series either click the link under the tags or look into my archive.Check out our Tumblr blog for progress updates and silly art - bonefucker-sanstasies.tumblr.com





	

**Author's Note:**

> based on yet another request we got on our blog, keep em comin guys CC; we're workin on the rest as hard as we can, tho bein newly in college and gettin back into work after a two week vaycay is definitely one huge obstacle for our creative process :o but we'll push through! we always do B)  
> if you were the kinky soul who requested Sans in lingerine, let us know what you think of this! hope we met your standarts and images well enough CC;

“Sans?” The amused intonation of your voice makes the skeleton open one eye to look at you from the corner of his eye socket. You’re both in the elevator, the smell of his cup of coffee that he’s holding in one hand filling the small room. Far off you can hear the noon chiming of the large clock in the lobby.

“what is it, hun,” he asks, closing his eyes again and taking a lazy sip. You reach out and grab at the light pink hem poking from under his badly tucked in shirt. Sans almost spits out his coffee, looking down at your hand startled.

“Are you wearing frilly underwear?” Sans grins widely, blushing.

“...mmmmmmmmmaybe?” he chuckles, rubbing his skull. You laugh in disbelief, pulling at the rim of his pants to get a better look at the pink panties with a tiny white bow in the front.

“Oh my god, Sans!” you laugh, “why are you wearing these?” Sans shrugs, a bit flustered.

“heheh, i had no clean underwear left. i had to borrow these since paps ain’t home to wash the clothes.” He tucks his shirt in better to hide them, winking at you. “not that i would mind. but we’ll have to ask undyne to return him soon, or we’ll all drown in my dirty socks.” You cover your mouth and keep laughing.

“Oh Sans, aren’t you just full of surprises.” He just chuckles, shrugging. You just smile for a moment until another thought comes to your mind.

“Huh… I don’t remember owning these.” Sans shifts his eyes away before looking at you mischievously.

“who said i borrowed them from you?” he chuckles deeply, his bones rattling. You look at him in disbelief.

“Papyrus?!” you ask, gasping with another laugh when Sans nods.

“he had a bunch of other pieces i could’ve borrowed, but these were the cutest.” He takes another sip of his coffee. “of all the nonbinary monsters i know, paps probably gives the least shit about gender norms.” You nod, smiling.

“And it’s a good thing, too,” you mutter, “I like how you guys don’t mind being feminine. It’s pretty cute, even hot, sometimes.” Sans doesn’t answer, just giving you a side glance as he takes another sip. The elevator beeps as it reaches its stop. The door opens and both of you walk out, stopping at a water cooler a few steps away. Sans finishes his coffee in one big gulp, handing you the cup.

“thanks for the kicker, honey,” he nods, giving you a small kiss on the cheek, “but my break is almost over. i’ll see you at home.”

“Wait!” you stop him, he looks at you in question. You lean in and give him another kiss on the teeth. “Okay, you may proceed, hun,” you laugh. Sans smiles widely.

“i love you honey.”

You smile back. “I love you too.”

  


Then Sans disappears, teleporting back to his own workplace a few miles away. You stay by the watercooler for a few more minutes before grabbing the mug and walking off to wash it and get back to your office. You forget all about your elevator conversation in just an hour or two of working.

It’s a really long shift, but finally you manage to finish your work, get in your car and drive home. You’re a bit tired, looking forward to getting home and maybe clean up a bit before Sans arrives later in the evening. Since Papyrus went to look after Undyne’s and Alphys’s kids while they’re on their second honeymoon your house has been turning into such a mess. Maybe you could find some bad movie online for you and your skeletal sweetheart to watch after he gets home. Hmm, should you order pizza? It always took a bit longer for it to get to your house since it was run by a family of slime monsters. They made some amazing pizza though.

You get out of your car, all sorts of thoughts running through your head. You reach into your pocket, fishing out your keys, but just as you’re about to grab the knob, the door slightly opens before you. You’re a bit startled, wondering what’s going on. There’s dim light and the smell of scented candles… But something else catches your attention. It’s Sans’s voice, saying a simple “ _come on in_ ”. You smile widely, already getting a good idea of where this is going.

You push the door open and find a trail of rose petals. You have to chuckle, just how cheesy can you get? But, the room is rid of dirty clothes and ketchup stains. Looks like Sans really did do more than just prepare something special, which actually amazes you much more than just the romantic gesture.

You take your shoes off, closing the door behind you, hanging your coat up and slowly following the trail. It leads around the couch, up the stairs, and right to your bedroom. You can’t help but smile like an idiot the whole time you’re approaching whatever it is that Sans has prepared in there. You go up the stairs and straight to your door only to have it once more click open for you before you can touch the knob. You slowly push it open, noticing all the candles and decorations before you spot your skeleton lover amongst it all.

You kind of can’t believe what you’re seeing.

Sans lays on your bed posed on his side, leaning his head on one hand with his legs folded one over the other. His head is turned away, facing low, his eyes closed. When you approach, he laxly lifts his eyelids and turns to you with a calm, even seductive look.

Draped over his bones is a set of expensive looking royal blue frilly lingerie.

You stare at him smiling, absolutely speechless. Sans grins back, before speaking up.

“waddup,” he says in voice completely out of place for the mood. You have to laugh at his nonchalant ever present joking. He waits for you to finish laughing, turning your attention back to him, before he reaches out a hand to you.

“come here sweetheart,” he says in a voice that matches a little better. You smile, accepting his invitation.

You come to him, taking his hands into yours and looking down at him, Sans returning your smile with one of his own. Without any words you kneel down so your heads are at the same height and you take in the blue lingerie your skeleton lover put on. Only now that you're close enough do you notice that all the lace has a small skull patterns on it and you can't help but giggle. _Of course_ he'd pick that.

“like what you're seein'?” Sans asks and you look up at him, just silently nodding. “of course you do, it’s the _skoolest_ piece there was, ” he grins widely and you giggle, but he quickly comes back to his previous calm look. “would you like me to make you feel as good as this looks?” he asks slowly, almost seductively, despite already knowing the answer.

Instead of answering and stating the obvious, you strengthen your hold on Sans's hands, pressing them against the bed and leaning in. You press your wet lips against his mouth and he lets out a shaky breath, not expecting such a hungry reaction. You stick your tongue between his teeth, running it over the inside of them, his breathing getting faster and louder in response. When you can feel his magical tongue forming inside, you pull back and he whimpers, but does nothing to stop you. You lick your lips as you look at him, one of his eyes closed as he tries to calm his breathing, faint blue glow coming from his mouth.

“I'd like it very much,” you say and he gives you a confused look for the few seconds it takes him to realize you're only now answering his previous question. He chuckles, shaking his head, smirking at you while he breaks his hands free from yours only to entangle your fingers. He sits up on the bed and pulls at you, getting you down on your back and straddling your thighs. He never lets go of your hand in the process, now bringing it close to his face, only to press his teeth against it in such a soft, loving way. He stays like that for a few moments, eye sockets closed, before he pulls back, putting your hand down on the sheets.

The look he gives you afterwards makes you know shit's going down and it's gonna feel amazing.

Sans stares down at you with his eyes half lidded, so calm, so loving. You smile up at him, lifting your hands up and gently grabbing onto his hipbones, he responds to your smile, lifts his arms up and puts his hands behind his skull, showing his body off to you. You rub his hipbones absentmindedly with your thumbs, looking up and down his skeletal body. You love the way the soft fabric cascades over his ribs. Sans grins wider when he sees how mesmerized you are by the show.

"heh, hope i'm doin’ a good job over here," he says in a deep half whisper, "i ain't the best gal around, ya know..." You raise your eyebrows at him.

"What are you talking about? You look great!" Sans puts his hands down on your chest, cupping your boobs absentmindedly.

"yeah, but, ya know... still ain't got that ladylike charm i guess. paps can pull it off so easily, but he doesn't have an accent as thick as a femur bone, heh." You smile wider, suddenly surprising him by sitting up. You hold him in your arms, squishing him closer, intentionally getting his hands rammed into your cleavage.

"Aw shush, sweetheart," you say in a more feminine friendly manner. Usually you talk with Sans more as your best friend, so you figure a little change of approach could make him get into this role more. "You're very cute, and _very_ charming. I mean, just all of this," you gesture to the clean room filled with rose petals and scented candles. You don't even finish your sentence, just smiling at him before grabbing onto the lingerie’s frilling gently. You pull him closer, kissing him a bit more dominantly. He kisses you back while you run your hands up and down his back, over his spine, from his ribs to his hipbones. He attempts to touch you back, but you hold his wrists, giving him a little dominant smirk. His calm expression is slowly changing into a flustered one as you caress him while restraining his hands, gaining more and more power over him.

When you decide you've asserted yourself enough, you grab onto him and lift him up, setting him down on the bed. Before he can do anything you're already looming over him on your hands and knees. Sans seems a little nervous, his face blue. You figure he's a bit unfamiliar with this kind of situation and decide to help him out some more.

Trailing the back of your finger over his cheek gently you look down at him, benevolent but completely in charge. Then, slowly, you lean in to where his ear should be. You rub your lips over his temple before speaking in as deep of a voice you can manage.

_"You're such a good girl..."_

Sans freezes up, then a soft whimper escapes him with a weak shudder coming up his spine. You pull back, grinning widely down at him. A huge flustered smile takes over his face as he looks away shyly. Finally, his blue eyes shine your way and he smiles a bit shyer, smile growing.

"i think it's safe to say... _wowie,_ " he imitates his brother and you have to laugh. You kiss him all over his teeth again before going south, lips moving over his neck, spine, and collarbones.

“Let me know if something doesn’t feel right,” you mutter as you place wet kisses over his bones. You know he'd never hold anything back, but better safe than sorry as they say. And then, you'd never forgive yourself if you did anything he wouldn't enjoy.

You can hear a quick reply before Sans starts whimpering as you take his clavicle between your teeth, the contact of bone on bone making soft, clicking noises. You smile to yourself as his quiet noises reach your ears, getting a little louder as you move your mouth sideways down the bone, switching between licking and giving it soft nibbles. It's when you reach the end and your lips hit the shoulder strap of Sans's lingerie that you start moving down, kissing your way over the lace fabric. You lean down so you have better access, sticking your butt up in the air in an almost cat-like way. Just one look at Sans from beneath your eyelashes lets you know he's been watching your every move. His expression is a mixture of anticipation, lust and love and you're ready to give him everything... in just a bit.

You give him a few more kisses over the fabric covering his body, your hands running down his arms until they reach the wrists. As you slowly pull away, sitting back over his femurs, you press at the wrists slightly to let him know he's to keep them down until you tell him to. You rise up on your knees a little, closing your eyes and taking the hem of your shirt into your hands as you pull it up over your head, shaking it around to get your hair back into place. When you open your eyes again to look at him, his eye sockets are half closed, as if his mind froze. Good thing you're here to turn up the heat a little bit.

“Sans, dear,” you say to get his attention from your chest and up to where your eyes are. He breathes a quick _huh, yeah?_ and you give him the sweetest, most innocent smile you got. “Would you be so kind as to help me take off my bra?”

He looks at you unsurely and you can tell he's almost afraid to move his hands because of before. You smile at him, nodding to let him know it's okay, that there isn't any sort of catch. Right away he smiles back and stretches his hands out for you, propping himself up on his elbow so he can reach better. He's almost got the clasp in his fingers when you take hold of the backside of his ribs, rubbing over it with your nails. He gasps, missing the clasp and letting out a low grunt as you move your hands about.

“Is there a problem, Sans?” you ask with played curiosity, grinning widely.

“n-no, i just-- aah!” You trail your nails down over his vertebrae, his words melting into deep moans.

“Come on, sweetheart, we ain't got all day,” you tease him again, grabbing hold of the tip of his hipbone, tilting your head to the side. Sans grins, nervous but excited, playing along. Despite you playing with his sensitive spots he manages to take your bra off and you slip it off of your arms, throwing it aside. Pushing Sans back down you get up on your knees, looking down at him with a dominant smirk as you grab on the zipper of your jeans, popping the button open. You slide them down to your knees, then lean down to get them off completely, hovering over Sans’s face as you do and looking closely into his bright eyes. Once your pants are gone, only your underwear keeping you modest. You lean down and give your skeleton lover a kiss for good measure, just so he doesn’t have to wait long without any contact. You kiss for a moment, lickin on his teeth and fondling your tongue over his. Pull up again you pull your underwear off, sitting down over his pubis and smiling down at him.

Sans has a big flustered smile over his face, enjoying the pressure on his pelvis. Unformed raw magic emanating from it, tingling your bits a little, making you giggle. Sans’s hands come up your legs to grab your hips, but once he reaches for your crotch you stop him.

“Hey, I thought I made it clear for you to lay back.” Sans looks a little confused, blinking up at you.

“oh, uh, i just- i thought i’d give ya a dick ya know…” You shake your head.

“What for? I don’t need one this time.” Sans’s confusion is only joined by slight disappointment.

“but… i thought i was gonna be the lady tonight…” You smirk wider.

“And you will be,” you growl, and he looks up at you, eye arches raised in question. “Come on Sans, we don’t need a dick to have fun do we?” You wink at him and he shifts his eyes away, his face getting even more flushed and blue.

“w-wow, you- ya mean… damn,” he chuckles, “holy shit i mean - i’m so up for this. come on, don’t leave me waitin’ hun.” You smirk wider.

“Now now, don’t be so impatient…” You begin to shift back, until you’re between his legs. Grabbing onto his femurs you lift them up, setting down between them while Sans watches you excitedly. You smile at him sweetly, leaning your head down between his legs and rubbing your face over the bulge of unformed magic under the soft fabric. Soon you grab onto the hem with your teeth and pull them down a bit before pushing them aside with your thumb. Sans lets out a whiny moan of pure excited anticipation as you hover your smiling mouth over his newly formed magic bits.

The blue of his magic glistens in the light of the candles. “So beautiful, _perfect,_ ” you whisper to yourself as you can't tear your eyes from it and it's Sans's moan that brings your attention back to his face. A hard blue blush spreads down his cheekbones as he nibbles on the fingers of his hand while the other is desperately clutching at the sheets. He's breathing hard, his magic twitching with every inhale he takes. The look makes you all the more hungrier for Sans, to make him feel so good he won't able to handle it, until he breaks down so wonderfully he forgets his own name.

And you know just where to start.

You run your palm over his femur as you look down between his legs, wetting your lips with your tongue as you slowly lean down. His breathing hitches for a second as your lips touch his ilium, placing slow, wet kisses in a trail, moving downwards. When you're close enough to feel the vibrations of his magic on your chin you stop, listening to his quiet whimpers. Only when you can recognize the words _please please, go on, please_ do you finally move on, opening your mouth and moving it from the bottom to the top of his slit. Sans lets out a long, deep growl, his hips moving into your face as you repeat the motion, sticking your tongue deeper between the lips every time you do so. His bones are quietly rattling as they want to move against you more, his body wanting to go deeper and well, you can't say no to that beautiful, messed up face.

You grab onto his femurs, hooking them around your shoulders and without any warning you rise up, taking his body with you until it’s only his shoulders and head that's left lying on the bed. You sit on your heels and move your hands under his pelvis and spine to keep him steady. From this position you have an excellent view of him just as well as he can see everything you're doing. Just from the change alone you can feel the magic under you getting hotter than before.

“Let me hear you, babe,” you whisper with a smile before burying your tongue between his folds. Immediately Sans opens his mouth wide and provides you with exactly what you asked for. In return you reward him with closing your lips around his clit and suck on it and circle it with your tongue, feeling hard trembles running down his spine.

It doesn't take long before all your attention brings Sans to climax, his eyes wide and mouth open as he cries out, even thrashing around a little, not knowing what to do with himself. All of it on display for you to see. Your tongue gets coated in his blue juices as you carefully and gently lick all of it up.

You hold him before he calms down again, slowly putting him back down onto the bed. His cheeks still blue, his breathing not yet normal as you run your eyes over his body, smiling at the cute underwear once more.

You give him a while to relax, gently rubbing his femur up and down as you lay beside him on your side, supporting your head with your hand, watching his breath become calmer and calmer. After a few minutes he slowly opens his eyes and looks up at you, smiling, his face still flushed.

“babe… that was great,” he whispers, reaching a hand up to pet your hair with the back of his hand. “hope there’s more where that came from, heheh.” You smirk down at him, kissing his hand when he comes up to pet your cheek.

“You bet, my sweet pretty girl.” It feels kind of funny to call him that, but Sans seems ecstatic about the feminine pet names. You slowly get up on your knees and hands, crawling on the bed until you’re over him again.

“My sweetheart,” you kiss him on the forehead softly. “My hunnybun,” you give him another smooch on the edge of his nose bone. “My _turtle dove._ ” Sans’s eyes brighten up at that last one, and you can feel his shaking breath on your lips as he whimpers. He can’t even put his adoration in words, so you just lean down and kiss him on the teeth.

You engage in a long drawn out kiss, slowly coming from simply rubbing your lips over his teeth to gently fondling your tongues together, licking his teeth, humming in comfort. You are leaning on your elbows on the sheets while he rubs his arms over you, up from your shoulders all the way down your back to your butt repeatedly. It feels so natural, so soft, so full of love, and _so damn hot_. Soon your knees are shifting back until your crotch presses against him, making you both moan softly into each others mouths.

Your bits are already pretty wet, although nowhere near as wet as Sans’s. You pull back from the kiss, his tongue rolling back into his mouth as he looks up at you, all flustered and out of breath, a big smile spread over his teeth. You smile back, gently rubbing your crotch over his, trying to get your loins involved, which is not easy from this angle. Sans loves the small amounts of friction you’re giving him, but you decide it’s your turn to get some, too.

“Sweetie, would you mind letting go? I want a different position.” Sans lets go of you immediately.

“of course darlin', whatever you want.” You get up from him and he lifts himself up on his elbows to see what you’re up to. You pull back behind his legs, grabbing onto them to direct his movements. You put one down on the sheets and the other up, spreading his legs and uncovering his bits completely as you finally remove the lacy underwear making him cover his mouth, a little shy. You smile down at him as you lift one leg making his eyes go wide when he realizes what you’re up to. You put your thigh over his on the sheets, your other leg going under his. You let him watch for a bit, letting the position he’s in sink in, before gently rubbing your crotches together under this new angle.

A soft moan escapes him as you move yourself against him, his legs spreading as wide as they can go invitingly. You can't help but smile, seeing him splayed under you, a small streak of saliva running down his cheek, his eyes blown wide with pleasure, love, and need.

It only makes you hungrier for this, for him.

You shift a little and take better hold of his leg, pulling it up before to get closer to him, pressing it to yourself and hugging it to your body. Sans's breath hitches when you drag your teeth down his tibia, his magic lightly tingling against your crotch with need as he so wants you to continue.

Again you begin rocking your hips and yeah, this feels so much better, your hands squeezing around Sans's femur as you repeat your movements, the wet noises from where you touch gradually getting drowned by Sans's rising voice. Just one look at him tells you he's already so lost in the feeling, his hands clutching at the sheets over his head as he tries his best to not move against your orders.

“Sans,” you call for him and he immediately turns to you, focusing on your face. “ _Sans_ , you're so good for me,” you stress your words with a grunt as you thrust harder than before and he whines both at your words and what you are doing to him. “This feels so incredibly good, do you feel it too, Sans?” you ask even though you know he's too far gone to answer you. Not to mention you're more than sure about how he feels anyway.

That's why his voice coming out in a higher pitch as he tries to speak surprises you so much.

“it fee- nnaah!” Sans whines, but you can see he's trying to tell you something and you slow down your movements, unable to stop entirely at this point. “it feels so fucking good,” he manages to say between fast paced breaths. “and it's all you,” he continues, “your everything is so amazing and so perfect and- HNGHHH!!”

Despite cutting him off mid-sentence with a hard thrust, you can't help yourself but give him all you got, making this as good for both of you as possible. After all, he deserves every bit of it, and you're more than willing to give him all he desires. You pay attention to his reactions as you look for the rhythm and angle that makes him cry out louder than others, the heat of your own pleasure slowly clouding your thoughts and leaving only lust to drive you on.

You end up leaning lower over him, rubbing your clit against his, mindlessly rocking back and forth. You can feel both your and his wetness in the heat between you, your loins buzzing with pleasure. Sans has his eyes closed, one hand clutching the bed sheet over his head and the other holding onto the blue lingerie at its fringe. He moans and gasps as you go on, unable to keep your own voice down anymore. You lean down even lower and he gasps from the added pressure, his eyes shooting open and going wider. You messily kiss his lower jaw, pressing your lips onto his teeth, sharing your breath as you get closer.

You can feel the femur that you’re holding onto twitch as Sans’s body arches under you, unable to fight your weight. He moans and whimpers, eyes rolling back and tearing up with pleasure as he comes. Just the sight of him like this is making you weak all over, the weakening feeling twitching through you as you come just moments after him, letting out a loud moan.

Then it goes silent again. Both of you lay there, still tangled together, feeling one another's warmth and slowly catching your breath. Gently you let go, both of you exhaling deeply once you untangle your legs from him. Your hand tenderly held by him as he looks up at you. You lay down beside him and for a while both of you are quiet, just relaxing from the high. You feel Sans gently slip his fingers between yours, smiling at the loving gesture.

After a moment Sans moves closer, his arms reaching around you. You open your eyes and smile at him as he leans in close and presses his teeth into your cheek.

“that was great,” he whispers, “like damn…” He kisses you again and you reach your arms around him too, kissing him back. For a few more minutes you lay there hugging, then you lift your head, looking around at all of the lit candles.

“Sans, darling, we shouldn’t fall asleep with all these candles still-”

Sans just lazily raises a hand and swings it lightly, a gust of air putting out all of the candles at once. You chuckle to yourself and snuggle him closer.

“You’re so lazy,” you grin. He just smiles back before the two of you slowly fall asleep.

**Author's Note:**

> This is part 21 of a series that has some sort of continuity going on, for the whole series either click the link under the tags or look into my archive.


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